An enzyme (ADA, EC 18.104.22.168, 363 aa) that deaminates adenosine and 2′-deoxyadenosine to inosine or 2′-deoxyinosine respectively. An autosomal recessive defect in ADA causes 20–30% of cases of severe combined immunodeficiency (SCID) and was the first candidate disease for gene replacement therapy. A deficiency of ADA causes an increase of dATP, which inhibits S-adenosylhomocysteine hydrolase; S-adenosylhomocysteine accumulates and is lymphotoxic. See also ADAR. Adenosine deaminase complexing protein 2 (ADCP2, dipeptidyl peptidase IV, EC 22.214.171.124, conversion factor, 766 aa) forms a complex with ADA and generates the tissue-specific forms. It is a serine exopeptidase that cleaves X-proline dipeptides from the N-terminus of polypeptides, an intrinsic membrane glycoprotein. ADCP1 is known, but there is some doubt whether it is actually involved in ADA complexes. Adenosine deaminase, tRNA-specific 1 (ADAT1, 502 aa) is involved in editing tRNA and deaminates adenosine-37 to inosine in eukaryotic tRNA(ala).
Subjects: Medicine and Health — Chemistry.